1. Field of the Invention
This invention relates generally to the field of wireless communications. In particular, the invention relates to wireless communication systems capable of providing an emergency beacon.
2. Related Art
Disasters and emergency situations are unpleasant events that have affected humanity throughout history. They range from natural disasters to individual emergencies. Occasionally, they involve individuals being trapped underneath materials such as sand, rubble, snow and mud in situations involving sand storms, crumbling structures, avalanches or mudslides, respectively. Typically, these are examples of life threatening situations and any device capable of providing quick and accurate location of a person trapped in these types of situations will greatly improve the chances of rescue and survival of the person.
Past attempts to satisfy this need have included utilizing an emergency beacon device. However, emergency beacon devices are very specialized devices that are typically found only in military and commercial equipment such airplanes and marine vessels. Emergency beacon devices are not readily available for utilization by individuals. Therefore there is a need for a device capable of providing this type of information that is available to individuals.
The worldwide utilization of wireless devices such as two-way radios, pagers, portable televisions, personal communication system (“PCS”), personal digital assistants (“PDAs”) cellular telephones (also known a “mobile phones”), Bluetooth, satellite radio receivers and Satellite Positioning Systems (“SPS”) such as Global Positioning Systems (“GPS”), also known as NAVSTAR, is growing at a rapid pace. As the number of people employing wireless devices increases, the number of features offered by wireless service providers also increases, as does the integration of these wireless devices in other products.
The number of features offered by wireless service providers is increasingly matching the features offered by traditional land-line telephone service providers. Features such as call waiting, call forwarding, caller identification (“caller I.D.”), three-way calling, data transmission and others are commonly offered by both land-line and wireless service providers. These features generally operate in the same manner on both wireless devices and land-line telephones.
Presently, emergency beacons are not available in wireless devices but an attempt at providing location information of a wireless device user in an emergency situation is the Enhanced 911 (also known as E911) service. E911 is an example of an approach of providing a location of a person utilizing a cellular telephone in an emergency situation in, a similar fashion that a 911 service call (normally referred to as a “911” call) does on a land-line telephone. However, E911 operate differently on wireless devices than a 911 service call does on land-line telephones.
When a 911 call is placed from a land-line telephone, the 911 reception center receives the call and determines the origin of the call. In case the caller fails, or forgets, to identify his or her location, the 911 reception center is able to obtain the location from which the call was made from the land-line telephone switching network and send emergency personnel to the location of the call.
If instead, an E911 call is placed from a wireless device such as a cellular telephone, the E911 reception center receives the call but cannot determine the origin of the call. If the caller fails, or forgets, to identify his or her location, the E911 reception center is unable to obtain the location of the call because the mobile switching network is different than the land-line telephone switching network. At present, the best that the E911 reception center may possibly do is determine the location of the basestation corresponding to the cell from which the call was placed. Unfortunately, typical cells in a cellular network system may cover an area with approximately a 30 mile diameter.
However, the United States Congress, through the Federal Communications Commission (FCC), has enacted a requirement that cellular telephones be locatable to within 50 feet once an emergency call, such as an E911, is placed by a given cellular telephone. This type of position data would assist police, paramedics, and other law enforcement and public service personnel, as well as other agencies that may need to have legal rights to determine the position of specific cellular telephone. Therefore, there is a need for a system that determines the location of a wireless device within 50 feet once an emergency call such as an E911 is placed by a given wireless device such as a cellular telephone.
A proposed solution to this problem has been to utilize a wireless positioning system that includes satellites and/or pseudolites (such as basestations) to triangulate the position of a wireless device such as a cellular telephone. GPS is an example of a SPS that may be utilized by a wireless device in combination with an appropriate GPS receiver to pinpoint the location of the wireless device on earth. The array of GPS satellites transmits highly accurate, time coded information that permits a receiver to calculate its exact location in terms of latitude and longitude on earth as well as the altitude above sea level. The GPS system is designed to provide a base navigation system with accuracy to within 100 meters for non-military use and greater precision for the military (with Selective Availability ON).
The space segment of the GPS system is a constellation of satellites orbiting above the earth that contain transmitters, which send highly accurate timing information to GPS receivers on earth. The fully implemented GPS system consists of 21 main operational satellites plus three active spare satellites. These satellites are arranged in six orbits, each orbit containing three or four satellites. The orbital planes form a 55° angle with the equator. The satellites orbit at a height of 10,898 nautical miles (20,200 kilometers) above earth with orbital periods for each satellite of approximately 12 hours.
Each of the orbiting satellites contains four highly accurate atomic clocks. These provide precision timing pulses used to generate a unique binary code (also known as a pseudo random or pseudo noise “PN” code) that is transmitted to earth. The PN code identifies the specific satellite in the constellation. The satellite also transmits a set of digitally coded ephemeris data that completely defines the precise orbit of the satellite. The ephemeris data indicates where the satellite is at any given time, and its location may be specified in terms of the satellite ground track in precise latitude and longitude measurements. The information in the ephemeris data is coded and transmitted from the satellite providing an accurate indication of the exact position of the satellite above the earth at any given time. A ground control station updates the ephemeris data of the satellite once per day to ensure accuracy.
A GPS receiver configured in a wireless device is designed to pick up signals from three, four, or more satellites simultaneously. The GPS receiver decodes the information and, utilizing the time and ephemeris data, calculates the approximate position of the wireless device. The GPS receiver contains a floating-point processor that performs the necessary calculations and may output a decimal display of latitude and longitude as well as altitude on the handset. Readings from three satellites are necessary for latitude and longitude information. A fourth satellite reading is required in order to compute altitude.
However, while E911 approaches are a beginning in the attempt of determining the location of a wireless device user, the 50 foot accuracy required by the FCC is not accurate enough for an emergency beacon application because a person may be trapped beneath a type of life threatening material such as sand, rubble, earth, snow or mud that requires immediate rescue. Additionally, E911 solutions require the wireless device user to actively select the E911 service. However, in many emergency situations the wireless device user may be trapped or injured in a way that the wireless device user will not be able to actively activate any type of service including E911.
Therefore, there is a need for a system capable of producing an emergency beacon signal in a wireless device that is accurate and capable of being activated even if the wireless device user is incapacitated. Moreover, there is a need for system capable of producing an emergency beacon signal in a wireless device for an extended period of time on a typically wireless device power source such as a battery.